Waveform generator



May 29,1'195'6 y 1. 'MARON ET AL 2,748,275

wAvEFoRM GENERATOR Filed June 29. 195s' 2 sheets-sheet 1 /NPuT PULSE *'1;

JNVENTOR. IRVINE MAREIN E: HERBERT 5.BRIIIAUINELL ouTPl/TZ BY TTORNEY VOLTA GE May 29, 1956 Filed June 29, 1955 l. MARON ETAL 2,748,275

WAVEFORM GENERATOR 2 Smets-Sheet 2 oar/Dur one l OSC/ll TUR INI/'ENT DI?.

IRVINEF MARDN En HERBERT 5. ERDADWELL /ITTORNEY United States Patent WAVEFORM GENERATOR Irving Maron, Haddonfieid, and Herbert s. Bmdweu, Audubon, N. J., assignors to Radio Corporation ci' America, a corporation of Delaware Application June 29, 1953, Serial No. 364,788

15 Claims.` (Cl. Z50- 36) This invention relates to electronic circuits for generating waveforms, and more particularly to relaxation osnals in the time period of an operating cycle that may be initiated aperiodically.

Yet another object of this invention is to provide an improved waveform generator that reliably and economically produces a predetermined number of output signals in the time period of an operating cycle that is repeated periodically.

Waveforms generated by apparatus of this type may be in the form of signals for the control of various types of electronic or electromechanical apparatus. determined number of pulses may be produced and repeated at periodic or aperiodic time intervals; For example, the generated pulses may be used as sweep signals for a cathode-ray tube oscilloscope.

The aforementioned and other objects of this invention are achieved in 'an embodiment of this invention employing first and second relaxation oscillators that have higher andlower 'frequencies of oscillation, respectively. Each circuit includes a grid-controlled gas tube'with a resist- A preance-capacitance network coupled to the anode of the s tube, and the control grids biased below the critical grid voltages for full anode voltages. The critical grid voltage is the grid Voltage at which a gas. tube ignites for a predetermined anode voltage. The control grids of both tubes are interconnected.V When the gas tube lin the second circuit of lower frequency is conducting, its control grid is maintained above the critical grid voltage for the applied. anode voltage. Because of the direct connection, the control grid of the other tube is also above this critical grid voltage, and the first circuit, of higher frequency, oscillates. When the tubev in the second circuit extinguishes, the first circuit is inthe relaxed condition completing a cycle of oscillation, so that the potential at the' control grids of bothtubes falls to the bias potential. Thus, oscillation in the first circuit stops until the tube in thev second circuit is again rendered conductive. With a second control grid in the tube of the second, circuit biased above the critical voltage for full anode. voltage, this circuit may be made freely running; the rst circuit then oscillates during the conducting phase of the second circuit. With both control grids of this second circuit tube biased' below the critical voltages, the second circuit is stable and does not oscillate. A positive pulse applied to a control. grid of the tube in the second circuit renders the tube conductive. Oscillation in the 'rst circuit is ice then initiated and continues for the conductive time of the second circuit.

The novel features of this invention as well as the invention itself both as to their organization and mode of operation, may be better understood from the following description, when read together with the accompanying drawings, in which:

Figure 1 is a schematic circuit diagram of an embodiment of the invention;

Figure 2 is a graphical diagram of waveforms occurring at various portions of the circuit shown in Figure 1;

Figure 3 is a schematic circuit diagram of another embodiment of this invention; and

Figure 4 is a schematic circuit diagram of output wavef orms of the circuit shown in Figure 3.

' Referring now to Figure 1, there is shown a circuit diagram of an embodiment of this invention, in which a rst gas discharge tube 10 of the thyraton type is connected in a relaxation oscillator circuit 12. This oscillator circuit includes a rst and second anode resistor 14, 1,6 for applying a source of operating potential B+ to the anode 18 of the thyratron 10, a cathode load 20 connected between the cathode 22 and ground, and a first capacitor 24 connected from the anode 18 of the tube to ground. A negative biasing source 26 is connected to the rst control grid 28 of the tube through a grid resistor 30. The second control grid 32 is connected to the cath ode 22.

. A second gas discharge tube 34, also ofthe thyratron type, has a resistor 36 and a second capacitor 38 connected in series across the tube 34. Both control grids 40, 42 of the second thyratron 34 are connected together and also directly connected to the rst control grid 28 of the first thyratron 10. These control grids are all biased through the same grid resistor 30. An input terminal 44 is coupled to the rst control grids 28, 4'of both tubes 10, 34 through a coupling capacitor 46. An output terminal 48 is coupled to the cathode l22 of the rst tube `10 through a coupling capacitor 50. The second capacitor 38 is charged from B+ through a large resistor 52, and also through a third thyratron 54 shunting that resistor 52. The cathode 56 of the third thyratron 54 is connected to the second capacitor 38, and the anode 58 is connected to B+ through a small resistor 60. The first control grid 62 of the third thyratron, `is biased through a voltage divider formed of a pair of resistors 64, 66, which are connected between ground and the anode 18 of the rst tube. I

The negative bias on the control grids 28, 40, 42 of the first and second thyratrons 10, 34 is below the critical voltage corresponding `to full anode potential so that these tubes are extinguished in the standby condition of the circuit. The second capacitor 38 is normally fully charged to B+ so that there is no voltage drop across the third thyratron 54, and it is normally extinguished. The waveforms occurring at various portions of this circuit are shown in Figure 2. When a positive input pulse is applied to thecontrol grids of the first and second tubes 10, 34, both. tubes are fired. Current drawn through the second tube 34 discharges the second capacitor 38 through the anode resistor 36. The second tube continues to conduct until the anode voltage falls belowthe tiring potential, the period for which depends upon the time constant of the resistance-capacitance network. During `conductionin the second tube 34, a sheath of positive ions around the control grids 40, 42 maintains these grids near ground potential by causing current to dow through the grid resistor 30. Because of the interconnection with the grids of the second tube, the first control grid 23 of the rst thyratron 10 is also maintained near ground potential. With this grid potential, the circuit of the first tube 10 functions as a freely-running relaxation oscillator. The first capacitor 24 discharges until Ythe potential at the anode 18ct the first tube 10 falls below the firing potential, at which time the first tube extinguishes. The first capacitor 24 then recharges through the anode resistors 14, 16 until the `anode 18 is atthe firing potential again, at which time the tube retires'. These oscillations continue as long as the grid' potential is` above the critical voltage. When the second capacitor38 has sufficiently discharged to lower the anode potential of the second tube 34 below thefiring potential, the second tube goes out. This is arranged to occur while the first tube is extinguished, and the first capacitor 24 is recharging. This may be done by appropriate adjustment of the time constants in the resistance-capacitance networks. At this time, the control grids 28, 40, 42 of vboth the first and second thyratrons 10, 34 are returned to the negative bias potential. Thus, the first tube cannot refre and the oscillations are terminated. An output pulse is produced at the cathode 22 of the first tube each time that tube is fired.

The first capacitor 24 continues to recharge towards B+. At a predetermined intermediate potential level, the voltage on the first control grid 62 of the third thyratron 54 rises above the critical voltage; the tube fires to quickly recharge the second capacitor 38, and then extinguishes itself when the anode to cathode potential in insufficient to maintain conduction. The circuit is then in its initial standby condition, and ready to receive another input pulse to repeat the above described cycle.

The repetition rate of the output pulses is determined by the charge and discharge time constants associated with the first capacitor 24. The discharging time constant may be increased by inserting a small resistor (not shown) in the discharge path of the first capacitor, at the anode of the rst tube. Ordinarily, the resistance provided by the cathode resistor 20 is sufiicient for this purpose. The duration of oscillations in the oscillator circuit 12 is determined by the time constant of the discharge path of the second capacitor 38. Accordingly, the number of output pulses, for any predetermined repetition rate, may be varied by adjustment of the resistor 36 at the anode of the second tube. The vrestoration period of the entire circuit is determined by the recharge of the first capacitor Z4 to a voltage that is attenuated through the resistance divider 64, 66. The circuit is restored when this attenuated voltage exceeds the'critical grid voltage of the third thyratron 54. The recharge time of the second capacitor 38 by this tube 54 is relatively short, being limited only by the small resistor 60 at the anode of the third tube. The large resistor 52 connecting the second capacitor 38 to B+, insures that the second capacitor 38 remains fully charged for long periods of standby operation. Output signals may also be taken at the anode of the first thyratron. It should also be noted that a plurality of relaxation oscillators having different frequencies may be simultaneously controlled by the second thyratron 34, in the same manner.

An appropriate set of component values and potential values for a completely operative embodiment of this invention, are shown in Figure l. The tube type used with these components is 2D21. The specific components and values shown are only illustrative, not to be taken as a limitation on this invention.

The embodiment of this invention described above is stable in operation, and adapted for operation with input pulses applied at irregular intervals. This invention may also be used for periodic recurrence of the cycle of operation. A circuit for this purpose is shown in Figure 3. A fjrst thyratron 70 is connected in a first relaxation oscillator circuit 72 having a resistance-capacitance network, as described above; and a second thyratron 74 is similarly connected in a second relaxation oscillator circuit 76. The first control grids 78, 80 of both tubes are directly interconnected, and negatively biased through 4 v a grid resistor. The second control grid 82 of the second thyratron is connected to ground through a grid resistor. The negative grid bias is sufiiciently low to be below the critical voltage of the first tube 70 for full anode potential B+, and sufiiciently high for the second circuit 76 to be freely running. An input terminal 84 may be connected to the second control grid 82 of the second tube 74 for applying thereto positive synchronizing pulses having an amplitude sufiicient to initiate conduction in the second tube 74. Output signals may be taken from the cathodes of both tubes across cathode resistors.

The time constants in both circuits 72, 76 are arranged to provide a frequency of oscillation in the first circuit 72 that is greater than the frequency of oscillation in the second circuit 76. When a synchronizing pulse is received, the second tube 74 conducts, raising the potential at the first control grid 80. The potential at the first control grid 78 of the first tube rises above the critical voltage, and the tube fires. The first circuit oscillates as long as the second tube 74, is conducting as in the first-described embodiment. Upon the second tube 74 extinguishing, the oscillations in the first circuit 72 are terminated, and the capacitor 86 in the second circuit 74 is then recharged through an adjustable resistor 88 to complete a cycle. This second circuit 74 also operates as a relaxation oscillator, either synchronized or freely-running, and serves to gate the first circuit 72 to repeat the cycle. Thus, two trains of output signals are produced at the cathodes of the tubes; the one from the first circuit having a higher frequency than that from the second circuit, as lshown in Figure 4. These two sets of signals of different frequencies have various applications: forV example, they may be used as the vertical and horizontal sweep signals for a cathode-ray tube. y

It may be seen from the above description of this invention, that an improved waveform generator is provided that reliably produces a predetermined number of output signals in response to an input signal. It may also be used to produce a plurality of sets of signals having different frequencies. This circuit is economical in the components required, and is adapted for periodic and aperiodic operation.

What is claimed is:

l. A waveform generator comprising an oscillator circuit including a gas discharge tube having 'a control electrode, and means for controlling the oscillation of said oscillator circuit including another gas discharge tube having a control electrode, means providing a direct voltage connection between said control electrodes of said tubes to provide a tube-conductive-bias voltage at said control electrode `of said first-mentioned tube in response to conduction of said other tube, and circuit means connected to said tubes permitting periods of simultaneous conduction of said tubes, said circuit means including means for controlling the state of conduction in said other tube. Y

2. A waveform generator comprising an oscillator circuit having a predetermined frequency of oscillation, said oscillator circuit including a gas discharge tube having a control grid electrode, and means for determining the duration of oscillation of said oscillator circuit including another gas discharge tube having a control grid electrode, means providing a direct voltage connection between said control grid electrodes of said tubes to provide a tubeconductive-bias voltage at said control electrode of said first-mentioned tube in response to conduction of said other tube, and circuit means connected to said tubes permitting periods of simultaneous conduction of said tubes, said circuit means including means for determining the duration of conduction in said other tube.

3. A waveform generator comprising an oscillator cir cuit having a predetermined frequency of oscillation, said oscillator circuit including a gas discharge tube having a control grid electrode, and a first capacitor; means for determining the duration of oscillation of said oscillator circuit including' another gas discharge tube havinga control grid electrode, means providing a; direct voltage connection between said control' grid electrodes of'said tubes to controll the voltage at said control electrode of said first-mentioned tube in accordance with the voltage at the other of said control electrodes, and means including a second capacitor for determining the duration of conduction in said other tube; and means responsive to the charge of said irst capacitor for changing the charge in said second capacitor. p

4. A waveform generator as recited in claim 3 wherein said means responsive to the charge of said iirst capacitor for changing the charge in said second capacitor includes an additional gas discharge tube having a control grid electrode coupled to said lirst capacitor, and another electrode coupled to said second capacitor.

5. A waveform generator comprising a plurality of oscillator circuits having dilerent frequencies of oscillation, each of said circuits including a gas discharge tube having a control grid electrode, and means providing a direct voltage connection between said control grid electrodes of said tubes to maintain the voltage at said control electrode of said tubes at or above a predetermined critical voltage when the other of said tubes is conducting.

6. A waveform generator comprising a plurality of oscillator circuits having different frequencies of oscillation, each of said circuits including a gas discharge tube having an anode, cathode and control grid electrode, and including a capacitor coupled to said anode of the respective tube, said circuits further including means for biasing said control grids below the critical voltages thereof, means providing a direct voltage connection between said control grid electrodes of said tubes to maintain the voltage at said control electrode of said tubes at or above a predetermined critical voltage when the other of said tubes is conducting, and output means coupled to at least one of said anode and cathode electrodes.

7. An electronic circuit comprising a plurality of gas discharge tubes each having an anode, cathode and control grid electrode, separate resistancecapacitance networks connected to said anodes of said tubes and permitting periods of simultaneous conduction of said tubes, means providing a direct voltage connection between said control grids of said tubes to provide a tube-conductive-bias voltage at said control electrode of said first-mentioned tube in response to conduction of said other tube, and output means coupled to at least one of said anode and cathode electrodes.

8. An electronic circuit comprising a first gas discharge tube having an anode, cathode and control grid electrode, means for applying a bias potential to the control grid of said first tube below the critical voltage thereof, and means for maintaining the potential at the control grid of said first tube at the critical voltage for a predetermined period, said maintaining means including a second gas discharge tube having an anode, cathode and control grid electrode, means providing a direct voltage connectionv between said control grid electrodes of said tubes to main.

tain the voltage at said first tube control electrodes at or above a predetermined critical voltage responsive to conduction in said second tube, and circuit means connected to said tubes permitting periods of simultaneous conduction of said tubes, said circuit means including means for maintaining conduction in said second tube for a predetermined period.

9. An electronic circuit comprising a tirst, second and third gas discharge tube each having an anode, cathode and control grid electrode, a first and second capacitor respectively coupled to the anodes of said first and second tubes, means for applying a bias potential to said control grids of said tubes below the critical voltages thereof, means providing a direct voltage connection between said control grids of said first and second tubes to at` or above yit;predeterminecl critical voltage responsive vto conductionin said second tub'e,', input means coupled to said control grids of said first and second tubes, and means respectively coupling, said control grid and cathode of said third tube to said first andl second capacitors.

l0. A waveform generator' comprising a first and second; gas discharge tube each having an` anode, cathode and control grid electrode, separate resistance-capacitance networks having different time constants coupled to the anodes of said tubes, means for applying a bias potential to said control grids of said tubes below the critical voltages thereof, means providing a direct voltage connection between said control grids to maintain the voltage at said first tube control electrode at or above a predetermined critical tube-conductive-bias voltage responsive to conduction in said second tube, said second tube having an additional control grid electrode, means for applying a bias potential to said additional control electrode of said second tube, and output means coupled to one of said anode and cathode electrodes.

l1. A waveform generator comprising a lirst gas discharge tube having a control electrode, and means for controlling the state of conduction of said tube including means for varying the anode-cathode voltage across said tube, a second gas discharge tube having a control electrode, means for supplying an anode-cathode voltage above the firing potential to said second tube during conduction in said rst tube and means providing a direct voltage connection from said second tube control electrode to said first tube control electrode to maintain the voltage at said lirst tube control electrode at or above a predetermined critical tube-conductive-bias voltage when said second tube is conducting.

l2. A waveform generator comprising a plurality of gas discharge tubes each having a control electrode, means for controlling the state of conduction of a first one of said tubes in accordance with the state of conduction of a second one of said tubes including means providing a direct voltage connection from said second tube control electrode to said first tube control electrode to maintain the voltage at said first tube control electrode at or above a predetermined critical tube-conductive-bias voltage when said second tube is conducting, and circuit means connected to said tubes permitting periods of simultaneous conduction of said tubes.

13. A waveform generator as recited in claim l2 and further comprising means for biasing said iirst tube control electrode below said critical voltage.

14. A waveform generator comprising a plurality of gas discharge tubes each having a control electrode, and

means for controlling the state of conduction of a first one of said tubes in accordance with the state of conduction of a second one of said tubes, said controlling means including means providing a direct voltage connection from said second tube control electrode to said rst tube control electrode to maintain the voltage at said rst tube control electrode at or above a predetermined critical voltage when said second tube is conducting, means for biasing said first tube control electrode below said critical voltage, said second tube having a second control electrode, and means for applying pulses to said second control electrode to render said second tube conducting.

l5. A waveform generator comprising a plurality of gas discharge tubes each having a control electrode, and means for controlling the state of conduction of a tirst one of said tubes n accordance with the state of conduction of a second one of said tubes includingmeans for applying to said iirst tube control electrode an increase in voltage appearing at said second tube control electrode due to said second tube being rendered conductive, said voltage applying means connecting said second tube control electrode to said lirst tube control electrode to provide a tube-conductive-bias'voltage at said control electrode of said first-mentioned tube in response to conducmaintain the voltage at said rst tube control electrodes tion of said other tube, and circuit means connected to amm References Cited in the le of this patent UNITED STATES PATENTS Wolf Jluly 29, 1941 8 I -Iadeld May y5, 1942 Woodruff Apr. 19, 1949 Taylor Aug. 22, 1950 Burns July 22, 1952 

